Method of making imperforate deck panel with flush tie-down fittings



H. F. BRINKER ETAL METHOD OF MAKING IMPERFORATE Sept. 22, 1959 2,904,881

DECK PANEL WITH FLUSH TIE-DOWN FITTINGS Original Filed Feb. 28, 1956 2 Sheets-Sheet 1 uvvsmrms HARRY E am/wrm and JOHN CLARK,

Allorney Sept. 22, 1959 H. F. BRINKER ET 2,904,881

METHOD OF MAKING IMPERFORATE DECK PANEL WITH FLUSH TIE-DOWN FITTINGS Original Filed Feb. 28, 1956 2 Sheets-Sheet 2 I6 I) 2 l9.

INVENTORS HARRY F. ERIN/(El? and Attorney United States Patent METHOD OF MAKING IMPERFORATE DECK PANEL WITH FLUSH TIE-DOWN FITTINGS Harry F. Brinker, Whitaker, and John Clark, Munhall, Pa., assignors to United States Steel Corporation, a corporation 'of New Jersey Original application February 28, 1956, Serial No. 568,368. Divided and this application August 16, 1957, Serial No. 678,655

1 Claim. (Cl. 29- 475) This invention relates to a method of making a panel adapted to be laid in the hull of an aircraft carrier to constitute the flight and hangar decks thereof.

This is a division from our copending application Serial No. 568,368, filed February 28, 1956.

It is essential to provide the flight and hangar decks of aircraft carriers with tie-down fittings for securely anchoring airplanes maneuvering thereon. The fittings must be recessed or flush in order to leave the deck flat and unobstructed. The deck panels are quite thick (up to 2") and are composed of specially treated alloy steel, in order to afiord the high strength desired for sustaining airplane-wheel loads and resistance to battle damage by explosive blast or projectiles. The provision of the necessary recesses for flush tie-down fittings thus poses a difficult problem.

One method which has been used is to cut holes in the panels, forming the Wall of each hole as the frustum of an inverted cone, and weld therein a cup-shaped forged plug having cross bars extending across the top thereof. This method is laborious, costly and time-consuming. A more serious objection is the weakening of the panels resulting from the cutting of the holes, and the low resistance of the welded-in plugs to being blown through the holes by blasts occurring above the deck.

We have invented a novel method of making a deck panel which fully overcomes the aforesaid objections, and a method by which such panels may be readily manufactured. Our method is based on the discovery of a practice whereby the plates used for making the panels, despite their considerable thickness and great hardness and tensile strength, may be die-drawn cold to provide the necessary recesses. The resulting panel is entirely free from holes, the original metal thereof remaining unbroken at all points when manufacture is completed. The panel comprises a plate having die-formed depressions spaced therealong, each depression comprising a bottom which has the shape of a spherical segment and a rim in the form of a portion of an annulus. More specifically, the depression has the smoothly curved shape of a surface of revolution obtained by revolving about a vertical axis a segment of a circle concave upwardly and symmetrical relative to the axis, with a minor reverse curve at each end thereof. A cruciform forging or cross bar is laid in each depression and welded to the plate flush with the upper surface thereof;

In making our panel, we roll steel of suitable composition to a plate of the desired thickness, shear it to size, heat-treat it by quenching and tempering, flatten it cold and then subject it to cold die-drawing to form the depressions, after which the panel is ready for laying in the hull. The cruciform forgings or cross bars may be welded in place either before or after the panel is laid. The dies are shaped to form a smoothly curved reverse bend or hump in the plate around the rim of the depression as the latter is drawn. This temporary overdeforrnation is controlled to compensate precisely for the springback which occurs as the die pressure is released, leav- 2 ing the plate in its original condit f flatness, except for the areas of the depressions.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the draw- 1ngs:

Figure l is a plan view of a panel made according to our invention, with the mid portion broken out;

Figure 2 is an edge view thereof partly broken away;

Figure 3 is a plan 'view, to enlarged scale, of one of the depressions in the panel and the area immediately surrounding it;

Figure 4 is a partial section taken along the plane of line lV-IV of Figure 3;

Figure 5 is an elevation partly broken away, showing the cooperating punch and die for forming the depressions in the plate;

Figure 6 is a side elevation showing the stationary platen or base and the movable crosshead of a die-forming press having the die and punch of Figure 5 mounted therein, respectively, with the plate on the platen in transverse section; and

Figure 7 is an end elevation thereof.

Referring now in detail to the drawings and, for the present, particularly to Figures 1 through 4, our improved panel comprises a plate 1% of a length L, width W and thickness T, appropriate for use in the flight deck or hangar deck of an aircraft carrier, composed of a suitable alloy steel, has spaced depressions 11 formed therein in spaced rows parallel to the side edges thereof. A cruciform anchorage fitting or cross bar 12 overlies each depression and has its ends welded to the plate inwardly of the rim of the depression. Plate 10 may, for example, be 12 x 35 and up to 2" thick, rolled from nickel-chromium or nickel-chromium-molybdenum steel. The depressions 11 may conveniently be about 10" in diameter and about 1.5" deep at the center.

The depressions are bowl shaped, i.e., they are defined by a smooth gradual curve in all directions and are free from sharp bends and corners. Each depression includes a bottom portion 11a which is a segment of a sphere, concave upwardly, and a rim zone 11b, convex upwardly, which is a portion of the surface of an annulus, the continuation of which is indicated in broken lines at 13 in Figure 4. The radius R of the sphere of which portion is a segment should be about 3.5 times the thickness T. The radius R of the section of the annulus of which zone 11b is a part should be about 2.5 times the thickness T. These ratios give a depression having a depth approximating T. g

It will be evident that the interior and exterior of the depression are surfaces of revolution formed by rotating curves A-A and A'A', respectively, about axis X-X. Each of these curves includes a principal central circular are symmetrical relative to the axis, with a minor reverse curve at each end. This conformation results in smooth, easy and uniform flow of metal in the stretching caused by the shaping dies, with stress and tendency toward cracking or tearing. The deformation eifected by die-drawing causes a reduction in the thickness of the metal between the center and rim of the depression, e.g., from 1.75 to 1.5".

Cross bar 12 has radial arms round in section which are beveled at the ends on the lower side as at 14, to fit snugly in the depression and on their upper sides. as at 15 to form a V-notch with the interior of the depression, to receive a deposit of weld metal 12a. When the cross bars are thus installed, ample clearance is afforded between them and the bottoms of the depressions to admit the terminal hooks of securing lines.

The apparatus and method by which we are enabled to produce the panels described above will now be explained with reference more particularly to Figures 5 through 7. A heat of the desired alloy steel is made and teemed into ingots. Each ingot, after being cropped, is reduced to a plate of the required thickness by rolling in conventional blooming, slabbing and plate mills. The rolled plates are sheared to size and given a heat-treatment by quenching from a temperature above the critical point and tempering to develop their maximum hardness and tensile strength consistent with the mini mum ductility required for tour ness. The exact details of such treatment will vary depending on the composition of the steel used, but such details are known to skilled metallurgists and therefore require no elaboration. After heat-treatment, the plates have a Brinell hardness of about 235 and a tensile strength of about 112,000 p.s.i. They are then flattened in a leveler or forging press. The heat-treated, flattened plates are then subjected to repeated cold die-drawing to form the depressions 11 individually at the desired locan'ons. At all times after heat-treatment, the plates must be kept below 500 F. to prevent disturbing their quenched and tempered condition, except at the welds where only small areas are involved.

The depressions are formed by the successive application to the plates of the forging dies shown in Figure 5, of which the male or punch 16 is mounted on the slide or crosshead 17 of a conventional forging press 18 of high capacity, and the female die or matrix 19 rests on the base or platen 20 thereof. The punch fits in a trough in the slide and is adjustable therealong by virtue of being carried by through. bolts 21 extending through slots in the slide and the upper portion of the punch. The matrix fits in a trough in base 20 and is slidable therein by means of ropes 22 attachable thereto, one at a time, and to one end of the slide. The ropes are trained around sheaves 23 so that a pull in one direction or the other will be exerted on the matrix when one rope is attached thereto, by raising the slide. Posts 24 upstanding on base 20 guide movement of the crosshead toward and from the base. Screw shafts 25 threaded through the posts at one end of the press carry push blocks 26 for accurately positioning a plate suspended between the punch and matrix as shown in Figures 6 and 7, by suitable traveling cranes on opposite sides of the press. When the plate has been properly spotted, closure of the punch on the matrix draws the metal of the plate and forms a depression 11.

Punch 16 has a nose 16a which is a segment of a sphere, and a frusto-conical shoulder 16b. The nose and shoulder are connected by a smoothly curved surface which is a portion of an annulus. The radius of the sphere and the radius of the section of the annulus should be about 3T. Matrix 19 has a central cavity 1% which is a segment of a sphere, and a frusto-conical shoulder 1% connected thereto by an annular surface. The radius of cavity 19a should be about 3.5T and the radius of the section of the connecting annulus in the neighborhood of T.

When the punch is brought down on the plate, after applying a suitable lubricant in the area to be deformed, the frusto-conical shoulders 16b and 19b impart a temporary reverse curvature to the plate in the area thereof bordering the depression, as the metal is deformed by die-drawing. In other words, a slight excess deformation is effected to compensate for the natural spring-back of the metal as the punch is withdrawn. This leaves the plate fiat within a small tolerance, in the area surrounding the depression, instead of slightly dished as it would be otherwise. The cross bars are secured in place by arcwelding inthe known manner..

Our invention is characterized by numerous advantages. In the first place, it provides an imperforate deck panel free from holes which are a potential source of weakness under blast, even though closed by welded-in plugs. Despite the thickness and great strength of the plate, the integral depressions can be safely formed by proper dies and a forging press of the required capacity. The mild cold-working of the plate by the dies in the regions of the depressions does not impair the physical properties of the metal. Cold dierawing preformed as described, after heat-treatment and flattening, with compensation for springback, furthermore, avoids disturbing the flat condition originally imparted to the plate except, of course, for the depressions themselves. The smooth curvature of the dies at all points minimizes any tendency to tear or crack the metal during drawing.

The cross bars are wholly below the plate surface, can easily be fixed in place with a minimum of welding, and are well adapted to withstand heavy shock loads such as are imposed by the wheel of an airplane in landing. They are also suited for mass production. Damage to the cross bars by blast will not result in projections above the deck level to foul arrestor lines or hooks.

Although we have disclosed herein the preferred practice of our invention, we intend to cover as Well any change or modification therein which may be made without departing from the spirit and scope of the invention.

We claim:

The method of making an armor-plate deck panel having a tensile strength of the order of 100,000 p.s.i. and a hardness of the order of 235 Brinell, with tie-down fittings for aircraft spaced therealong which consists in rolling a mass of armor-plate steel to a thickness of the order of 2 inches, heating the resulting plate to a temperature above the critical point for said steel, quenching the plate from said temperature and tempering it substantially to said hardness, then cold flattening the hardened plate, cold die-drawing a plurality of bowl-shaped depressions in the hardened plate at locations spaced therealong, welding a bar transversely of each depression and maintaining all portions of the plate, except those adjacent the welds, at temperatures below 500 F. subsequent to said tempering, thereby preserving the physical properties of the main body of the plate substantially unimpaired from the quenched and tempered condition.

References Cited in the file of this patent UNITED STATES PATENTS 1,126,838 Nichols Feb. 2, 1915 1,168,982. Walker Jan. 18, 1916 1,745,153 Dalton Jan/28, 1930 2,052,063 Wenn Aug. 25, 1936 2,106,647 Neck Jan. 25, 1938 2,427,756 West Sept. 23, 1947 2,610,587 Pietzsch Sept. 16, 1952 2,776,474 Melcher Ian. 8, 1957 

